1. Field of the Invention
The present invention relates to an improved sealing element which includes an energizer element and a solid plastic element which forms a sealing surface.
2. Description of the Related Art
Seal elements are commonly utilized in machines having parts which move relative to each other and which include fluid which is to be retained in a specific portion of the machine. Seal elements may additionally be utilized between static members of machines in situations in which a fluid is to be kept within a certain portion of the machine. One of the machine parts typically includes a gland which is designed to house the sealing element. Examples of such seals include the annular seals utilized in hydraulic mechanisms to seal between the piston and the cylinder of the hydraulic mechanism. In these configurations, the gland may be formed in the piston or the cylinder of the hydraulic element.
Prior seal elements have included plastic sealing surfaces which cover the entire sealing surface of the seal. These plastic seal elements were in some cases made from polytetrafluoroethylene (PTFE).
Many known sealing arrangements utilize a two piece configuration with an energizer/seal element being first placed in the gland and a second separate sealing element then being placed adjacent the energizer/seal element. Configurations of this type are problematic in that they are difficult to install. Two piece configurations are additionally problematic as the additional seal parts create additional gap tolerance concerns.
What is need in the art is a seal arrangement having improved leakage control, reduced friction, and increased lifetime for sealing environments adapted for reciprocation, rotary, oscillating, and static uses.
What is needed in the art is a seal arrangement which allows a portion of the seal to contact the surface to be sealed and which is able to create controlled and non-linear load patterns at the point of seal contact.
The present invention is directed to overcome the above-mentioned shortcomings in the art, and provide a sealing apparatus with the unique construction that tends to prohibit seal rotation during operation with superior fluid film control. The present invention is in two parts. First is that of an elastomer energizer, which may be in the shape of a square ring, o-ring, or an other custom design for energizing the seal system. Second is that of a seal element having a particular geometry and composition.
The geometric layout of the seal element ensures firm contact between the seal and groove bottom, independently of the seal pressure and radial position of the moving part, and concentrates contact forces against the moving part by means of a seal apex. In the installed state, the seal is forced into contact with the groove bottom by having an outer diameter matching or exceeding that of the groove bottom, and a radial height exceeding that of the housing groove. Further, the influence of the compression ring or energizer is balanced out by positioning the seal apex near the axial position of the center of the energizer. The seal apex itself is defined by an inlet angle upstream of the apex of preferably more than 30xc2x0 to the moving part, and a downstream slip angle of greater than 5xc2x0 preferably greater than 7xc2x0.
Depending upon the geometry of the seal, the sealed pressure produces a net torque on the angular seal, which works to force the assembly down upon the moving part, or alternatively to improve contact with the groove bottom. The direction and relative magnitude of this improvement can be approximated by the ratio of radial groove height divided by the axial distance from the seal apex to where the seal meets the groove bottom. When the ratio exceeds one, seal contact with the groove bottom is improved with pressure, and in the present invention this ratio exceed 1.25.
In order to efficiently employ the above-described torque to control seal contact against the housing groove and the moving surface, the seal member must possess sufficient rigidity to limit the influences of deformation. The present invention is ensured by designing the seal in such a way that a straight line can be drawn from the seal apex through the solid body of the seal to the radial line defining the downstream wall of the seal, and that the first line forms an angle with the moving part of at least 40xc2x0, but possibly greater.
Flexibility to allow radial displacement of the moving part is determined by the radial height of the sealing element, defined as that portion of the seal element which lies downstream of the radial line going through the downstream end position of the energizer. In the present invention, a line can be drawn downstream from the point where this line intersects the moving surface forming an angle with the moving surface of at least 7xc2x0 without contacting the solid part of the seal.